In a power distribution system, a high-voltage wire used to supply high-voltage power and a low-voltage wire used to supply low-voltage power are included. Standard voltages and allowable ranges to allow a deviation from the standard voltages are defined for the high-voltage wire and the low-voltage wire. For this reason, a voltage drop is calculated by dividing the power distribution system from the substation to the load facility into a high-voltage system containing facilities such as the high-voltage wire and a switch and a low-voltage system containing facilities such as a low-voltage wire and a lead-in wire. Then, the voltage of the power distributed from the substation is set such that a voltage before and after the voltage drop remains in the allowable ranges of the high-voltage system and the low-voltage system, or the voltage of the power flowing through the power distribution system is adjusted by switching the switch disposed in the high-voltage system.
Patent Literature 1: Japanese Laid-open Patent Publication No. 10-70840
Patent Literature 2: Japanese Laid-open Patent Publication No. 2004-32983
By the way, as a distributed power source such as photovoltaic power generation comes into wide use, the distributed power source is provided in the customer in some cases. In this case, it may occur that a reverse power flows from the distributed power source disposed in the customer to the power distribution system of the electric power provider. Therefore, in a case where the power flows bidirectionally between the power substation and the load facility, for example, it may be considered that the power at each facility contained in the low-voltage system is significantly changed by the reverse power flow.
However, in the related art described above, there is a problem in that electrical connection of the power distribution system can be ascertained only in a rough unit of the high-voltage system and the low-voltage system. Therefore, in the related art described above, there is a concern that the abnormal situation is overlooked in a case where the power of the voltage exceeding the allowable range flows in a unit smaller than the high-voltage system and the low-voltage system.